This study utilizes a naturalistic human cross-fostering design to advance the understanding of childhood pathways to risk for drug use by identifying nuances in the rearing environment that are associated with child risk behaviors and competencies. In this quasi-experimental study, the sample will consist of 215 sibling pairs in which one sibling was reared from birth with an adoptive family, and the other sibling was reared from birth by the biological mother of the sibling pair. Similar to non-human cross-fostering studies, this design allows for the differentiation of the effects of the rearing environment from effect of shared genes between parent and child. The sample will be drawn from an existing study of adopted children and their biological and adoptive families (the Early Growth and Development Study; R01HD42608 and R01DA020585). We propose to add new data on 215 biological siblings of the adopted children. The biological siblings and their rearing parents will be assessed at the same age (age 7) and using the same measures that were used to assess the adopted children and the adoptive parents. The assessment includes child risk behaviors (e.g., externalizing problems, inhibitory control deficits) and social competencies (social skills, prosocial peer relations) known to be predictive of later drug use. The assessment of the rearing environment includes both risk-promoting (harsh parental discipline, parental drug use, conflictual partner relations, and parent psychopathology) and competence-promoting (e.g., parental sensitivity, warmth, effective monitoring, and warm marital relations) factors. To our knowledge, there is no other human cross-fostering study of social adjustment or parenting in childhood. The specific aims focus on the prevention of risk pathways leading to later drug use: (1) Compare risk behaviors and social competencies between the siblings reared apart; (2) Examine links between differences in siblings' rearing environment and differences in child adjustment; (3) Examine how positive rearing environments may buffer risk from children's inherited tendencies and how negative rearing environments may exacerbate inherited risk (GxE). The proposed study is well positioned to examine how the care giving environment differentially affects outcomes for siblings who are genetically-related, but who are reared from birth in different environments. The results will inform prevention efforts for reducing children's risk for later drug use by identifying facets of the rearing environment that are associated with child risk behaviors once shared genes between parent and children are removed, and rearing environments that might additionally offset inherited liabilities for early externalizing problems.